The LCD Power Supply Tester is designed for field use to diagnose possible power supply issues. Similar in function to a voltmeter but less accurate, it will tell you if the voltages coming out of each cable are within specifications. The advantage of this tester is that the power supply does not have to be removed from the computer, nor do the ground and power on pins have to be shorted. Also, the unit requires no batteries, no test leads, and is very compact in size. Several companies sell the exact same tester under different names, but from the pictures you can see they are all the same.